An optical screen such as a transmission type screen of a projection television usually comprises a lens sheet such as a Fresnel lens sheet or a lenticular lens sheet. In these years, a front panel may be attached to the surface of such a lens sheet for protecting the lens sheet.
As a base material of such a sheet for an optical screen, an acrylic resin is mainly used from the viewpoint of transparency. For example, JP-A-1-128059 discloses a lens sheet comprising an acrylic resin to which a methyl methacrylate base multilayer rubber is added. JP-A-9-302176 and JP-A-9-302177 disclose a lens sheet comprising a methyl methacrylate-styrene copolymer resin. Furthermore, JP-A-2000-66307 discloses a lens sheet comprising a methyl methacrylate-styrene copolymer resin to which a butadiene base graft rubber is added.
However, the lens sheets disclosed in JP-A-1-128059 and JP-A-2000-66307 have problems such that they tend to warp or deflect when they are used, stored or transported. The lens sheets disclosed in JP-A-9-302176 and JP-A-9-302177 have problems such that they tend to be cracked or chipped when they are processed or installed.